1. Technical Field
The present invention relates to an image processing device, an image processing method and a storage medium which stores an image processing program, and more particularly relates to an image processing device, image processing method and storage medium storing an image processing program that process images based on document data of which fabrication by photocopying is prohibited.
2. Related Art
With the spread of personal computers in recent years and rising capabilities of printers and photocopiers, a problem has arisen with illegitimate copying and illegitimate usage of confidential documents which are printed out, such as civil registry documents, contracts and the like.
Further, a technology has been proposed which, in order to synthesize larger amounts of additional information, splits the additional information into units of a certain length, generates a plurality of machine-readable code images, and synthesizes these into the background of the document.
Now, when the additional information is to be reconstructed from the machine-readable code images described above, it is desirable that the machine-readable codes appear on the paper in as complete a state as possible. Furthermore, because it is not possible to render both a latent image and a machine-readable code image in the same region, it is required that regions of machine-readable code images do not overlap with regions of a latent image.
However, the conventional technology gives no particular consideration to overlapping of the machine-readable code images with the latent image. Consequently, as shown in FIGS. 7A and 7B, when machine-readable code images are superposed with a latent image, there is a problem in that, of these machine-readable code images, only Codes 2 and 3 can be decoded, while the machine-readable code images of Codes 1 and 4 cannot be decoded.
Consequently, there is a possibility in that there may be machine-readable code images which cannot be decoded.